


For Science

by Anonymous



Category: Marvel Cinematic Universe
Genre: Anal Fisting, Established Relationship, M/M
Language: English
Status: Completed
Published: 2021-03-20
Updated: 2021-03-20
Packaged: 2021-03-29 00:54:39
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,413
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30148257
Author URL: https://archiveofourown.org/
Summary: They both loved to test limits.
Relationships: Peter Parker/Tony Stark
Comments: 1
Kudos: 7
Collections: Kink Lucky Dip





	For Science

**Author's Note:**

  * For [HogwartsToAlexandria](https://archiveofourown.org/users/HogwartsToAlexandria/gifts).



> Thanks to T for the beta.

They both loved to test limits.

Tony was used to being the one that gets the concerned looks from his friends when he’s being particularly reckless, going too fast for most other people to keep up with him. It’s been that way for years, which is why it feels like the world had been tilted on its side when he found Peter. For once, he’s not the reckless one in their friendship. At least not all the time, and he was delighted when Peter came around to work on a new science project, keeping up with his scientific babble without any expectation of him slowing down.

Tony had felt a thrill, a muted sort of sensation that hovered in the background of their interactions, when Peter’s face lit up at the next risky idea that popped into his head. Peter himself gave as good as he got, agreeing to work even more closely once he’d graduated high school — and as the years passed by, it soon slid into a romance, as natural as anything, with Peter being the first to press a kiss to Tony’s mouth in the heat of the moment.

Tony had responded back, pressing in the kiss, and after that, well, they were partners. Just on a more physical level that introduced some awesome perks in their relationship. It didn’t take long at all for the two of them to wonder just how much Peter’s body could take, spider-enhanced DNA and all. It was for purely scientific reasons, or that’s what he tried to say, before Peter laughed and played along, grinning all the while.

So, that’s how they ended up here, with Peter on his knees and Tony applying a liberal amount of lube on his hand, preparing himself.

It had been Peter’s idea in the first place, and after Peter brought up the concept of being fisted, Tony couldn’t let that idea go, no way.

He settled his left hand on the curve of Peter’s ass, just to grip something, as his right hand, lubed up and ready to explore, started to tease his rim, sinking a finger into him with ease. Peter’s face was down sideways against the mattress, but he can see half of his face, and how his eye is closing shut, his breathing even and steady.

“Get ready, Pete,” Tony said, knowing that right now, they haven’t done anything that isn’t new for Peter. Not that it’s bad. Not at all, in fact, there’s a steady sort of comfort with doing something as well practiced as fingering and opening the other one up, finger by finger.

Tony decided that it’s time to slide in another finger, and adding in the third shortly after, the lube doing the work of making it easier to get it inside him, even if Peter’s relaxing as much as he can. He moved his fingers now, finding that spot that made Peter draw in a sharp breath as he pressed into it.

“That feel good?” Tony teased, trying not to smile so soon. He saw Peter lift up his head a little, giving him as much of an amused glance as he can when looking to the side. Peter said, “I’m not sure about that. You might need to do that again, to get the clearest results.”

Tony nodded, playing along. He was a scientist, and examining the ways his partner could be physically stimulated was an especially fun topic to explore. He had lost count of how many times Peter had come off without a touch (a few memorable instances involved him talking Peter to an orgasm), or how well Peter could display his impressive strength when they were getting each other off (he loved how Peter could fuck him against the wall, that was novel), or even the times that they had creatively used Peter’s web shooters (it made for an interesting bondage experience).

Anyway, he was getting ahead of himself now that he was starting to stir just thinking about their past explorations with each other. He renewed his efforts, his eyes settling on how Peter’s slender cock was half hard, responding to each rub of attention that he gave his prostate. Tony did that for a while, until Peter finally asked him to continue.

“I don’t want to get distracted when you said you wanted to see what it was like to fist me,” Peter said, sounding almost apologetic. If you asked him, he would be happy to get Peter off like this, and had done so many times at the request of Peter, but Peter wasn’t wrong that he wanted to give proper fisting a go.

Dangling something like that in front of him had a similar effect to a cat being presented with a new treat.

It was time to add another finger, he decided.

Tony settled on his pinky finger, and moved it into Peter, slowly as if they had all the time in the world. They more or less did, but Peter would have words with him if he stretched it out — ahem — for much longer. He could see the pink flush that was now showing up on the back of Peter’s neck, his breath coming out stuttered, and his cock dripping precome from the amount of teasing he had given him. Tony wasn’t unaffected either, and he felt just as hungry for them to see it all the way through just as Peter had to be.

“Almost there,” Tony half whispered, his voice raspy. “You’re doing wonderful, Pete.”

He caught the glimpse of Peter smiling into the bedsheets, his hands lightly clenching the fabric, his whole body a perfect instrument for Tony to play on in the moment.

It’s just his thumb left now, and Tony shifted for a second, reaching for the bottle of lube to give it an extra coating, wanting to make sure that they have the greatest opening for success. His eyes are wide open when he pressed the meat of his thumb right against the rim of Peter’s hole, no doubt sparking all kinds of sensations for Peter right now. He even got to hear the sound of Peter making a soft whimper, barely anything, but so intensely full of want and need.

He could feel his cock straining against the confines of his pants to the point of being uncomfortable now, but it hardly registered when his focus was entirely on Peter, and trying to fill Peter up, beyond anything they had tried before. Tony felt his thumb catch right against Peter’s hole as he tucked it as much as he can against his other fingers, and it’s an almost impossibly tight squeeze, but slowly, very slowly, Tony felt something that was close to awe when he finally slid his hand all the way in, a perfect fit.

Peter’s eyes fluttered open and he has the familiar look of when he’s trying to keep himself together before he comes off. Tony felt an odd mixture of pride and undeniable lust as he moved his fist as much as he can. He never doubted that Peter would be able to do this the moment he brought it up.

It’s oddly vulnerable to have his hand all the way inside of Peter. Peter let out a heavy sigh, and Tony can see the way his brown hair is slightly messed up, a few strands resting against his forehead as his face has a pink tint to it.

Tony moved his fist, marveling at how well Peter is taking it, fucking him. He’s light-headed just watching it all, his knuckles pressing up against Peter’s prostate, which brings out the most wonderful-sounding sighs from Peter.

“Oh,” Peter gasped, as Tony pushed particularly hard with his fist. “Tony, I’m going to—”

Peter didn’t have time to finish his sentence before he cut himself off, eyes closing as an orgasm rolled over him, painting his bare stomach with come. Tony licked his lips, intensely aware of his own arousal and gently pulls his hand out of Peter, cleaning his hand with a nearby towel.

“Let me,” Peter said, moving to settle on his heels, facing Tony on the bed. Tony let him, settling his weight on his palms as Peter took hold of him in a familiar grip. It hardly took more than a few strokes before he spilled over, his hand closing over Peter’s.

Tony met Peter’s eyes with a smile. “We’re going to do another experiment, right, Pete?”


End file.
